Field of the Invention
Embodiments of the present invention relate to a photoelectric conversion apparatus and an information processing apparatus.
Description of the Related Art
A time of flight (TOF) method of measuring a distance to a target object by irradiating the target object with light and detecting reflected light from the object has been proposed as one of focusing methods. Specifically, the distance to the target object is measured on the basis of a period of time from a timing of the light irradiation until a timing of the reflected light detection (that is, a delay amount of the reflected light with respect to the irradiation light) and a light speed. At this time, since the reflected light from the target object is detected together with environment light corresponding to light in an external environment, a technology for performing the focusing while the environment light is taken into account is demanded.
FIG. 12 illustrates a configuration example of a light detecting element 1 according to a second exemplary embodiment of Japanese Patent Laid-Open No. 2005-303268 (in paragraph 0092 and subsequent paragraphs). The light detecting element 1 is provided with a first photosensitive unit 11a, a hole holding unit 13 corresponding to the first photosensitive unit 11a, a second photosensitive unit 11b, an electron holding unit 14 corresponding to the second photosensitive unit 11b, a recombination unit 15, and an output unit 16. The hole holding unit 13 holds holes generated by the first photosensitive unit 11a when a light source 2 is turned off (holes corresponding to the environment light). The electron holding unit 14 holds electrons generated by the second photosensitive unit 11b when the light source 2 is turned on (electrons corresponding to both the reflected light and the environment light from a target object 3). The recombination unit 15 causes recombination of the holes of the hole holding unit 13 (holes corresponding to the environment light) with the electrons of the electron holding unit 14 (electrons corresponding to both the reflected light and the environment light). As a result, the electrons corresponding to the reflected light among the reflected light and the environment light remain, and these electrons are read out by the output unit 16. According to this method, it is possible to obtain a signal corresponding to the reflected light among the reflected light and the environment light, which is advantageous to perform the focusing based on the TOF method at a high accuracy.
According to the configuration in which target carriers are taken out through the output unit 16 of the light detecting element 1 to detect the charge amount in accordance with the electrons and the holes as described in Japanese Patent Laid-Open No. 2005-303268, it is difficult to increase a read operation speed of the target carriers. For this reason, a focusing accuracy is not increased in a case where the focusing based on the TOF method is performed.
With reference to Japanese Patent Laid-Open No. 2005-303268 (paragraph 0045), such a structure is conceivable that a plurality of light detecting elements 1 each including the above-described respective units (the first photosensitive unit 11a, the second photosensitive unit 11b, and the like). According to this structure, the single light detecting element 1 corresponds to a unit pixel, and a signal for performing the focusing based on the TOF method is output from each of the light detecting elements 1, and a distance image is obtained as a result.
As one of methods of realizing this structure, two types of photodiodes are respectively used as the first photosensitive unit 11a and the second photosensitive unit 11b. For example, it is conceivable to use a photodiode composed of a P-type semiconductor region and an N-type semiconductor region surrounding the P-type semiconductor region as the first photosensitive unit 11a. For example, it is conceivable to use a photodiode composed of an N-type semiconductor region and a P-type semiconductor region surrounding the N-type semiconductor region as the second photosensitive unit 11b. At this time, in a case where these two types of photodiodes are used, a structure of a pixel needs to be designed while not only electric separation in the pixels of the two types of photodiodes but also electric separation from a photodiode in an adjacent pixel are taken into account. It should be noted that Japanese Patent Laid-Open No. 2005-303268 does not describe specific structures including which type of a circuit element to be used to construct which type of a circuit, how to realize the above-described respective units on a semiconductor substrate, and the like.